gfortran, DLL, underscore

Question

I want to access some subroutines from a third party DLL. The functions use STDCALL as the calling convention.

Running dumpbin /export foo.dll gives me some

Answer 1

You need to combine the use of ISO_C_BINDING with compiler attributes. You should really read the Mixed-Language Programming section of the gfortran manual. It gives good advice that can be used with other compilers as well. In particular, in your case you need the stdcall attribute:

interface VisBasSubs

   subroutine foo (DoubleArg)  bind (C, name="Foo")
      !GCC$ ATTRIBUTES stdcall :: foo
      use iso_c_binding, only: c_double
      real (kind=c_double), intent (inout) :: DoubleArg      

   end subroutine foo

end interface VisBasSubs

Notice the line with stdcall, it's what should make it work.